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The geared motor and pointer device are provided with a stopper mechanism
which restricts the range of movement of the trailing-side gear when the
trailing-side gear rotates in a counter-clockwise direction. In the
stopper mechanism, the part to be touched by the stopper comprises a
support-side protrusion which protrudes towards the center of rotation of
the trailing-side gear, and the width dimension in the peripheral
direction of the support-side protrusion is smaller on the inside in the
radial direction than on the outside in the radial direction. As a
consequence, even if the width in the peripheral direction of the
support-side protrusion is increased to a certain extent in order to
ensure strength, when the stopper mechanism is activated, the stopper
touching part and the part to be touched by the stopper come into contact
at a position close to the center of rotation of the trailing-side gear.

1. A geared motor comprising: a motor part; an output member; a gear
train comprising a plurality of gears structured to transmit rotation of
the motor part to the output member; a support member which supports the
motor part, the output member and the gear train; a stopper mechanism
which comprises a stopper abutting part provided in a first gear of the
plurality of the gears and a stopper abutted part provided in the support
member, the stopper mechanism being structured so that, when the first
gear is turned to one side in a circumferential direction, the stopper
abutting part is abutted with the stopper abutted part to restrict a
movable range of turning of the first gear to the one side; wherein the
stopper abutted part is an other side end part located on the other side
in the circumferential direction of a support body side protruded part
which is protruded from an outer side in a radial direction toward an
inner side in the radial direction and toward a turning center of the
first gear, and wherein a width dimension in the circumferential
direction on an inner side in the radial direction of the support body
side protruded part is set to be narrower than that on its outer side in
the radial direction.

2. The geared motor according to claim 1, wherein the first gear is
provided with a plate-shaped part in which teeth are formed on its outer
peripheral face and a body part which is protruded from the plate-shaped
part in a turning center axial line direction of the first gear at a
center of the first gear; and the stopper abutting part is an one side
end part located on the one side of a gear side protruded part which is
integrally formed with the body part on an outer peripheral face of the
body part.

3. The geared motor according to claim 2, wherein the gear side protruded
part is integrally formed with the plate-shaped part.

4. The geared motor according to claim 2, wherein the plate-shaped part
is formed with plate-shaped springs which are elastically abutted with
the support member in the turning center axial line direction of the
first gear at a plurality of positions in the circumferential direction,
and the gear side protruded part is formed at an angular position
corresponding to a portion between the plate-shaped springs adjacent to
each other in the circumferential direction.

5. The geared motor according to claim 4, wherein the support member
comprises a cylindrical tube part with which the plate-shaped spring is
abutted, and the stopper abutted part is integrally formed with the
cylindrical tube part on an inner side in the radial direction of the
cylindrical tube part.

6. The geared motor according to claim 1, wherein the plurality of the
gears comprises a second gear which is meshed with the first gear to
drive the first gear, and the stopper abutted part is provided at a
position where the first gear is applied with a reaction force in a
direction separated from the second gear when the first gear is turned to
the one side and the stopper abutting part is abutted with the stopper
abutted part.

7. The geared motor according to claim 6, wherein a turning angular range
of the first gear is divided into a first angular range and a second
angular range by an imaginary line passing through a turning center of
the first gear and a rotation center of the second gear, and in the first
angular range where the stopper abutting part is moved in a direction
coming close to the rotation center of the second gear when the first
gear is turned to the one side, the stopper mechanism is structured so
that the stopper abutting part is abutted with the stopper abutted part
in an angular range of 90.+-.60.degree. with respect to the imaginary
line when viewed from the rotation center of the first gear.

8. The geared motor according to claim 7, wherein the stopper mechanism
is structured so that the stopper abutting part is abutted with the
stopper abutted part in an angular range of 90.+-.10.degree. with respect
to the imaginary line when viewed from the rotation center of the first
gear.

9. The geared motor according to claim 1, wherein the first gear and the
output member are integrally turned with each other.

10. A pointer type display device comprising the geared motor defined in
claim 1, comprising a pointer which is held by the output member.

11. The pointer type display device according to claim 10, wherein a
stopping position by the stopper mechanism corresponds to a home position
of the pointer.

12. The geared motor according to claim 5, wherein the plurality of the
gears comprises a second gear which is meshed with the first gear to
drive the first gear, and the stopper abutted part is provided at a
position where the first gear is applied with a reaction force in a
direction separated from the second gear when the first gear is turned to
the one side and the stopper abutting part is abutted with the stopper
abutted part.

13. The geared motor according to claim 12, wherein a turning angular
range of the first gear is divided into a first angular range and a
second angular range by an imaginary line passing through a turning
center of the first gear and a rotation center of the second gear, and in
the first angular range where the stopper abutting part is moved in a
direction coming close to the rotation center of the second gear when the
first gear is turned to the one side, the stopper mechanism is structured
so that the stopper abutting part is abutted with the stopper abutted
part in an angular range of 90.+-.60.degree. with respect to the
imaginary line when viewed from the rotation center of the first gear.

14. The pointer type display device according to claim 11, wherein the
first gear is provided with a plate-shaped part in which teeth are formed
on its outer peripheral face and a body part which is protruded from the
plate-shaped part in a turning center axial line direction of the first
gear at a center of the first gear; and the stopper abutting part is an
one side end part located on the one side of a gear side protruded part
which is integrally formed with the body part on an outer peripheral face
of the body part.

15. The pointer type display device according to claim 14, wherein the
gear side protruded part is integrally formed with the plate-shaped part.

16. The pointer type display device according to claim 14, wherein the
plate-shaped part is formed with plate-shaped springs which are
elastically abutted with the support member in the turning center axial
line direction of the first gear at a plurality of positions in the
circumferential direction, and the gear side protruded part is formed at
an angular position corresponding to a portion between the plate-shaped
springs adjacent to each other in the circumferential direction.

17. The pointer type display device according to claim 16, wherein the
support member comprises a cylindrical tube part with which the
plate-shaped spring is abutted, and the stopper abutted part is
integrally formed with the cylindrical tube part on an inner side in the
radial direction of the cylindrical tube part.

18. The pointer type display device according to claim 10, wherein the
plurality of the gears comprises a second gear which is meshed with the
first gear to drive the first gear, and the stopper abutted part is
provided at a position where the first gear is applied with a reaction
force in a direction separated from the second gear when the first gear
is turned to the one side and the stopper abutting part is abutted with
the stopper abutted part.

19. The pointer type display device according to claim 18, wherein a
turning angular range of the first gear is divided into a first angular
range and a second angular range by an imaginary line passing through a
turning center of the first gear and a rotation center of the second
gear, and in the first angular range where the stopper abutting part is
moved in a direction coming close to the rotation center of the second
gear when the first gear is turned to the one side, the stopper mechanism
is structured so that the stopper abutting part is abutted with the
stopper abutted part in an angular range of 90.+-.60.degree. with respect
to the imaginary line when viewed from the rotation center of the first
gear.

20. The pointer type display device according to claim 19, wherein the
stopper mechanism is structured so that the stopper abutting part is
abutted with the stopper abutted part in an angular range of
90.+-.10.degree. with respect to the imaginary line when viewed from the
rotation center of the first gear.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a geared motor which is provided
with a stopper mechanism in its gear train and a pointer type display
device.

BACKGROUND ART

[0002] In a pointer type display device and the like, a geared motor
including a motor and a gear train disposed inside a case is used and a
pointer is fixed to an output member of the geared motor (Patent
Literature 1). In Patent Literature 1, the geared motor is proposed so
that a stopper mechanism is provided which is structured to stop a gear
at a home position where a pointer indicates the zero point. More
specifically, a structure has been proposed that, in a first gear
integrally turned with an output member and a second gear meshed with the
first gear for driving the first gear, a gear side protruded part is
provided at a substantially middle position in a radial direction of the
first gear and a support member side protruded part is provided in a
support member on an imaginary line passing through a turning center of
the first gear and a rotation center of the second gear and, when the
first gear is turned to the position where the pointer indicates the zero
point, the gear side protruded part and the support member side protruded
part are abutted with each other.

CITATION LIST

Patent Literature

[0003] [PTL 1] Japanese Patent Laid-Open No. 2001-327149

SUMMARY OF THE INVENTION

Technical Problem

[0004] However, when the pointer is returned to the home position and the
gear side protruded part provided in the first gear is abutted with the
support member side protruded part, the first gear is rebounded in a
reverse direction to cause the pointer to be shaken. In other words, in a
case that the pointer is to be returned to the home position, a gear
connected with the second gear, a rotor of a motor part and the like are
also turned and thus, when the stopper mechanism is operated and the
first gear is stopped, the second gear is also going to be stopped.
However, the second gear receives an inertia torque from the rotor and
the like in an opposite direction and the inertia torque is transmitted
to the first gear and, as a result, the first gear is rebounded.

[0005] Therefore, in view of the problem described above, an objective of
the present invention is to provide a geared motor and a pointer type
display device in which rebounding of a gear is restrained even when a
stopper mechanism provided in a gear train is operated.

Solution to Problem

[0006] To achieve the above mentioned objective, the present invention
provides a geared motor including a motor part, an output member, a gear
train including a plurality of gears structured to transmit rotation of
the motor part to the output member, a support member which supports the
motor part, the output member and the gear train, and a stopper mechanism
which includes a stopper abutting part provided in a first gear of the
plurality of the gears and a stopper abutted part provided in the support
member and is structured so that, when the first gear is turned to one
side in a circumferential direction, the stopper abutting part is abutted
with the stopper abutted part to restrict a movable range of turning of
the first gear to the one side. The stopper abutted part is an other side
end part located on the other side in the circumferential direction of a
support body side protruded part which is protruded from an outer side in
a radial direction toward an inner side in the radial direction and
toward a turning center of the first gear, and a width dimension in the
circumferential direction on an inner side in the radial direction of the
support body side protruded part is set to be narrower than that on its
outer side in the radial direction.

[0007] In the present invention, a width dimension in the circumferential
direction on an inner side in the radial direction of the support body
side protruded part is set to be narrower than that on its outer side in
the radial direction. Therefore, even in a case that the width in the
circumferential direction of the support body side protruded part is set
to be wide to some extent for securing strength, when the stopper
mechanism is operated, the stopper abutting part and the stopper abutted
part are abutted with each other at a position near the turning center
axil line of the first gear. Accordingly, when the stopper mechanism is
operated, collision energy applied to the first gear is small and thus
rebounding of the first gear can be restrained. Further, a movable range
to the one side of the first gear can be made wide.

[0008] In the present invention, it is preferable that the first gear is
provided with a plate-shaped part in which teeth are formed on its outer
peripheral face and a body part which is protruded from the plate-shaped
part in a turning center axial line direction of the first gear at a
center of the first gear, and the stopper abutting part is an one side
end part located on the one side of a gear side protruded part which is
integrally formed with the body part on an outer peripheral face of the
body part. According to this structure, the stopper abutting part (one
side end part of the gear side protruded part) is abutted with the
stopper abutted part at a position near the turning center axial line of
the first gear. Therefore, when the stopper mechanism is operated,
collision energy applied to the first gear is small and thus rebounding
of the first gear can be restrained.

[0009] In the present invention, it is preferable that the gear side
protruded part is integrally formed with the plate-shaped part. According
to this structure, the strength of the gear side protruded part can be
increased.

[0010] In the present invention, it is preferable that the plate-shaped
part is formed with plate-shaped springs which are elastically abutted
with the support member in the turning center axial line direction of the
first gear at a plurality of positions in the circumferential direction,
and the gear side protruded part is formed at an angular position
corresponding to a portion between the plate-shaped springs adjacent to
each other in the circumferential direction. According to this structure,
even when the plate-shaped spring is formed in the plate-shaped part of
the first gear, restriction of the position for forming the gear side
protruded part is small. Therefore, the gear side protruded part is
easily provided on an inner side in the radial direction.

[0011] In the present invention, it is preferable that the support member
includes a cylindrical tube part with which the plate-shaped spring is
abutted, and the stopper abutted part is integrally formed with the
cylindrical tube part on an inner side in a radial direction of the
cylindrical tube part. According to this structure, the strength of the
stopper abutted part can be increased.

[0012] In the present invention, it is preferable that the plurality of
the gears includes a second gear which is meshed with the first gear to
drive the first gear, and the stopper abutted part is provided at a
position where the first gear is applied with a reaction force in a
direction separated from the second gear when the first gear is turned to
the one side and the stopper abutting part is abutted with the stopper
abutted part. According to this structure, when the stopper abutting part
of the first gear is turned to one side in the circumferential direction
and is abutted with the stopper abutted part of the support member, the
first gear receives a reaction force in a direction separated from the
second gear. Therefore, engagement of the first gear with the second gear
becomes shallow and thus an inertia torque in an opposite direction from
the second gear is hard to be transmitted to the first gear. Accordingly,
rebounding of the first gear can be restrained.

[0013] In the present invention, it is preferable that a turning angular
range of the first gear is divided into a first angular range and a
second angular range by an imaginary line passing through a turning
center of the first gear and a rotation center of the second gear and, in
the first angular range where the stopper abutting part is moved in a
direction coming close to the rotation center of the second gear when the
first gear is turned to the one side, the stopper mechanism is structured
so that the stopper abutting part is abutted with the stopper abutted
part in an angular range of 90.+-.60.degree. with respect to the
imaginary line when viewed from the rotation center of the first gear.
According to this structure, when the stopper abutting part is turned to
one side in the circumferential direction and is abutted with the stopper
abutted part of the support member, the first gear is easy to receive a
reaction force in a direction separated from the second gear. Therefore,
engagement of the first gear with the second gear becomes shallow and
thus an inertia torque in an opposite direction from the second gear is
hard to be transmitted to the first gear. Accordingly, rebounding of the
first gear can be restrained.

[0014] In the present invention, it is preferable that the stopper
mechanism is structured so that the stopper abutting part is abutted with
the stopper abutted part in an angular range of 90.+-.10.degree. with
respect to the imaginary line when viewed from the rotation center of the
first gear. According to this structure, when the stopper abutting part
is turned to the one side in the circumferential direction and is abutted
with the stopper abutted part of the support member, the first gear is
further easily received with a reaction force in a direction separated
from the second gear. Therefore, engagement of the first gear with the
second gear becomes further shallow and thus an inertia torque in an
opposite direction from the second gear is hard to be transmitted to the
first gear. Accordingly, rebounding of the first gear can be restrained.

[0015] In the present invention, it is preferable that the first gear and
the output member are integrally turned with each other. According to
this structure, a movable range of the output member can be directly
restricted by the stopper mechanism.

[0016] The geared motor in accordance with the present invention may be
used, for example, in a pointer type display device and, in this case,
the pointer type display device has a pointer which is held by the output
member. In this case, it may be structured that a stopping position by
the stopper mechanism corresponds to a home position of the pointer.

Effects of the Invention

[0017] In the present invention, a width dimension in the circumferential
direction on an inner side in the radial direction of the support body
side protruded part is set to be narrower than that on its outer side in
the radial direction. Therefore, even in a case that the width in the
circumferential direction of the support body side protruded part is set
to be wide to some extent for securing strength, when the stopper
mechanism is operated, the stopper abutting part and the stopper abutted
part are abutted with each other at a position near the turning center
axil line of the first gear. Accordingly, when the stopper mechanism is
operated, collision energy applied to the first gear is small and thus
rebounding of the first gear can be restrained. Further, a movable range
to the one side of the first gear can be made wide.

BRIEF DESCRIPTION OF DRAWINGS

[0018] FIGS. 1a and 1b are explanatory views showing a geared motor to
which the present invention is applied.

[0019] FIG. 2 is a cross-sectional view showing a geared motor to which
the present invention is applied and which is cut at a position passing a
gear train.

[0020] FIGS. 3a and 3b are exploded perspective views showing a geared
motor to which the present invention is applied and which is viewed from
an output side.

[0021] FIGS. 4a and 4b are exploded perspective views showing a geared
motor to which the present invention is applied and which is viewed from
an opposite-to-output side.

[0022] FIGS. 5a, 5b and 5c are explanatory views showing a driven gear
which is used in a geared motor to which the present invention is
applied.

[0023] FIG. 6 is an explanatory view showing a planar structure of a
stopper mechanism which is structured in a geared motor to which the
present invention is applied.

DESCRIPTION OF EMBODIMENTS

[0024] A geared motor and a pointer type display device to which the
present invention is applied will be described below with reference to
the accompanying drawings. In the following descriptions, in a direction
where a turning center axial line "L" of an output member 10 is extended,
one side to which the output member 10 is protruded is referred to as an
output side "L1" and an opposite side (the other side) to the side where
the output member 10 is protruded is referred to as an opposite-to-output
side "L2". Further, an axial line of a rotor 5 in a motor part 1 is a
rotation center axial line "L0" and an axial line of a drive side gear 41
of a gear train 4 is a rotation center axial line "L5". Further, for
convenience, the one side of each of the rotation center axial lines "L0"
and "L5" is referred to as the output side "L1", and the other side of
each of the rotation center axial lines "L0" and "L5" is referred to as
the opposite-to-output side "L2".

(Entire Structure of Pointer Type Display Device)

[0025] FIGS. 1a and 1b are explanatory views showing a geared motor 100 to
which the present invention is applied. FIG. 1a is a perspective view
showing a geared motor 100 which is viewed from an output side "L1" and
FIG. 1b is a perspective view showing the geared motor 100 which is
viewed from an opposite-to-output side "L2". FIG. 2 is a cross-sectional
view showing the geared motor 100 to which the present invention is
applied and which is cut at a position passing a gear train 4. FIGS. 3a
and 3b are exploded perspective views showing the geared motor 100 to
which the present invention is applied and which is viewed from an output
side "L1". FIG. 3a is an exploded perspective view showing a state that a
second case member 22 is separated from a first case member 21, and FIG.
3b is an exploded perspective view showing a state that a gear train 4
and the like are detached from the first case member 21. FIGS. 4a and 4b
are exploded perspective views showing the geared motor 100 to which the
present invention is applied and which is viewed from an
opposite-to-output side "L2". FIG. 4a is an exploded perspective view
showing a state that the first case member 21 is separated from the
second case member 22, and FIG. 4b is an exploded perspective view
showing a state that the gear train 4 and the like are detached from the
second case member 22.

[0026] The geared motor 100 shown in FIGS. 1a through 4b is structured so
that a shaft-shaped output member 10 is protruded from a case 2 to the
output side "L1" in the turning center axial line "L" direction. The
geared motor 100 in this embodiment is used in a pointer type display
device 200 and, as shown in FIG. 1a, a pointer 11 is connected with the
output member 10.

[0027] The case 2 includes a first case member 21 formed in a
substantially circular shape when viewed in the turning center axial line
"L" direction and a second case member 22 formed in a substantially
circular shape when viewed in the turning center axial line "L"
direction. The second case member 22 is overlapped with the first case
member 21 from the output side "L1". The case 2 is a support member which
supports a motor part 1, the gear train 4 and the output member 10
described below.

[0028] The first case member 21 is provided with an end plate part 210 and
a side plate part 211 in a tube shape which is protruded to the output
side "L1" from an outer side edge of the end plate part 210. An outer
peripheral face of the side plate part 211 is formed with a hook 219 at a
plurality of positions in a circumferential direction. The second case
member 22 is provided with an end plate part 220 and a side plate part
221 in a tube shape which is protruded to the opposite-to-output side
"L2" from an outer side edge of the end plate part 220. An engaging
protruded part 229 is formed in the side plate part 221 at a plurality of
positions in the circumferential direction. Therefore, when the hooks 219
and the engaging protruded parts 229 are engaged with each other and the
first case member 21 and the second case member 22 are combined with each
other, the case 2 is structured. In the first case member 21, a protruded
part 212 which is, for example, used for fixing the geared motor 100 is
protruded toward the opposite-to-output side "L2" from the end plate part
210. Further, in the second case member 22, protruded parts 222 which
are, for example, used for fixing the geared motor 100 are protruded
toward the output side "L1" from the end plate part 220.

(Structure of Motor Part 1)

[0029] The geared motor 100 includes a motor part 1 in an inside of the
case 2. The motor part 1 is a drive source for the output member 10. The
motor part 1 is a stepping motor which includes a rotor 5 and a stator 6
disposed around the rotor 5. The rotor 5 is rotatably supported by a
support shaft 51. An end part on the opposite-to-output side "L2" of the
support shaft 51 is held by a shaft hole 213a formed in the end plate
part 210 of the first case member 21, and an end part on the output side
"L1" of the support shaft 51 is held by a shaft hole 223a formed in the
end plate part 220 of the second case member 22.

[0030] The rotor 5 includes a pinion 58 provided at an end part on the
opposite-to-output side "L2" in a rotation center axial line "L0"
direction and a magnet 50 formed in a cylindrical tube shape. An "S"-pole
and an "N"-pole are alternately formed at equal angular intervals on an
outer peripheral face of the magnet 50. In this embodiment, the magnet 50
and the pinion 58 made of resin are integrated each other by insert
molding. The stator 6 includes a stator core 60 provided with a plurality
of salient poles which face the outer peripheral face of the magnet 50
with a gap space therebetween. A coil 8 is wound around each of two
salient poles (main pole) of the plurality of the salient poles through a
coil bobbin 7. The stator core 60 is formed in a plate shape and is
structured by laminating a plurality of magnetic plates which are punched
in a predetermined shape. The stator core 60 is formed with a hole 68
through which a support shaft 410 of a drive side gear 41 described below
is penetrated. The coil bobbin 7 holds a plurality of terminal pins 70 to
which end parts of the coil 8 are bound and connected. An end part of the
terminal pin 70 is protruded to the output side "L1" through a hole 223d
which is formed in the end plate part 220 of the second case member 22.

[0031] The geared motor 100 includes a gear train 4 structured to
decelerate rotation of the rotor 5 and transmit it to the output member
10. In this embodiment, the gear train 4 includes the pinion 58, a drive
side gear 41 (second gear in the present invention) meshing with the
pinion 58, and a driven gear 42 (first gear in the present invention)
meshing with the drive side gear 41. The drive side gear 41 is provided
with a large diameter gear 411 meshing with the pinion 58 of the rotor 5
and a small diameter gear 412 coaxially formed with the large diameter
gear 411. The drive side gear 41 is rotatably supported by the support
shaft 410. An end part on the opposite-to-output side "L2" of the support
shaft 410 is held by a shaft hole 213b formed in the end plate part 210
of the first case member 21. An end part on the output side "L1" of the
support shaft 410 is held by a shaft hole 223b formed in a column part
226 which is formed in the end plate part 220 of the second case member
22. The driven gear 42 is provided with a plate-shaped part 43 in a
circular plate shape whose outer peripheral face is formed with outer
teeth 431 meshing with the small diameter gear 412.

(Structure of Driven Gear 42)

[0032] FIGS. 5a, 5b and 5c are explanatory views showing the driven gear
42 which is used in the geared motor 100 to which the present invention
is applied. FIG. 5a is a perspective view showing the driven gear 42
which is viewed in an oblique direction on the output side "L1", FIG. 5b
is a plan view showing the driven gear 42 which is viewed in an oblique
direction on the opposite-to-output side "L2", and FIG. 5c is a side view
showing the driven gear 42.

[0033] The driven gear 42 is a final gear structured to transmit its
rotation to the output member 10 and to be integrally turned with the
output member 10. The driven gear 42 is structured as described below.

[0034] In FIGS. 5a, 5b and 5c, the driven gear 42 is provided with a
shaft-shaped body part 44, which is protruded from the center of the
plate-shaped part 43 to the output side "L1", and a circular protruded
part 45 which is protruded from the center of the plate-shaped part 43 to
the opposite-to-output side "L2". A shaft hole 440, i.e., a through hole
into which the output member 10 is fitted is provided in the body part 44
and the circular protruded part 45. The driven gear 42 and the output
member 10 are integrally turned with each other.

[0035] The plate-shaped part 43 is formed with a groove 47 which
penetrates the plate-shaped part 43 in the turning center axial line "L"
direction. The groove 47 is extended to one side around the turning
center axial line "L" and then bent in a "U"-shape and extended to the
other side in the circumferential direction. As a result, a portion of
the plate-shaped part 43 which is surrounded by the groove 47 is formed
to be a plate-shaped spring 46 whose one end in the circumferential
direction is connected with the plate-shaped part 43. A protruded part
461 protruded toward the output side "L1" is formed on a tip end side of
the plate-shaped spring 46. In this embodiment, the plate-shaped spring
46 is formed at two positions with equal angular intervals in the
circumferential direction so as to extend in the same direction. An
angular interval of two plate-shaped springs 46 is 180.degree..

[0036] The plate-shaped part 43 is formed with a gear side protruded part
48 protruded to the output side "L1" and to an outer side in a radial
direction at an angular position between two plate-shaped springs 46 in
the circumferential direction. The gear side protruded part 48 structures
a stopper mechanism 9 which restricts a movable range when the driven
gear 42 is turned in a counterclockwise direction "CCW" (one side in the
circumferential direction) by abutting with a support body side protruded
part 28 described below.

(Support Structure for Driven Gear 42 and Output Member 10)

[0037] As shown in FIGS. 3a through 4b, the end plate part 210 of the
first case member 21 is formed with a cylindrical tube part 215 protruded
to the output side "L1" and a cylindrical tube part 216 protruded to the
opposite-to-output side "L2". The cylindrical tube parts 215 and 216 are
formed with shaft holes 215a and 216a which turnably support an
opposite-to-output side end part of the output member 10.

[0038] On the other hand, the end plate part 220 of the second case member
22 is formed with a cylindrical tube part 225 which is protruded to the
output side "L1". The cylindrical tube part 225 is formed with a shaft
hole 225a which turnably supports an output side portion of the output
member 10.

[0039] A face on the opposite-to-output side "L2" of the end plate part
220 of the second case member 22 is formed with a cylindrical tube part
227 into which the body part 44 of the driven gear 42 is entered and
plate-shaped ribs 224 which are extended from the cylindrical tube part
227 toward outer sides in a radial direction. An inner diameter of the
cylindrical tube part 227 is larger than an outer diameter of the body
part 44 of the driven gear 42, and an inner face of the cylindrical tube
part 227 does not contact with the body part 44 of the driven gear 42.
The ribs 224 are formed at four positions with equal angular intervals
around the cylindrical tube part 227. Three ribs 224a, 224b and 224c of
four ribs 224 are connected with the side plate part 221 and the
remaining one rib 224d is connected with the column part 226 formed with
the shaft hole 223b.

[0040] In this embodiment, the circular protruded part 45 of the driven
gear 42 is abutted with the cylindrical tube part 215 of the first case
member 21 and movement of the driven gear 42 to the opposite-to-output
side "L2" is prevented. Further, the protruded parts 461 of the
plate-shaped springs 46 of the driven gear 42 are elastically abutted
with an end face on the opposite-to-output side "L2" of the cylindrical
tube part 227 of the second case member 22 and movement of the driven
gear 42 to the output side "L1" is restricted. Therefore, the driven gear
42 and the output member 10 are restrained from rattling in the turning
center axial line "L" direction.

(Operations)

[0041] In the geared motor 100 and the pointer type display device 200
structured as described above, when electrical power is supplied to the
coil 8 through the terminal pins 70 in a state that the pointer 11 is
stopped at the zero point (home position), the rotor 5 is rotated and the
rotation is transmitted to the output member 10 through the gear train 4.
Therefore, the pointer 11 connected with the output member 10 is turned
in the clockwise direction CW. In this case, an angular position of the
pointer 11 is changed by inputting a predetermined number of drive pulses
into the coil 8 and, after the pointer 11 is turned to a target position
in the clockwise direction CW, the pointer 11 is stopped. Further, when
drive pulses for reverse rotation are supplied, the pointer can be turned
in the counterclockwise direction CCW to another target position.

(Structure of Stopper Mechanism)

[0042] FIG. 6 is an explanatory view showing a planar structure of a
stopper mechanism 9 which is structured in the geared motor 100 to which
the present invention is applied. In FIG. 6, the gear train 4 is shown by
the solid line and the second case member 22 is shown by the alternate
long and short dash line.

[0043] In FIG. 6, in the geared motor 100 in this embodiment, a stopper
mechanism 9 is structured between the driven gear 42 and the second case
member 22 (support member) so that, when the pointer 11 shown in FIG. 1a
is turned in the counterclockwise direction CCW and reached to the home
position indicating the zero point, a stopper abutting part 91 provided
in the driven gear 42 is abutted with a stopper abutted part 92 provided
in the second case member 22 to restrict a movable range in the
counterclockwise direction CCW (to one side around the turning center
axial line "L") of the driven gear 42.

[0044] In this embodiment, the driven gear 42 is provided with a gear side
protruded part 48 protruding toward an outer side in the radial direction
on an outer peripheral face of the body part 44 which is protruded to the
output side "L1" from the plate-shaped part 43 at the center of the
driven gear 42. The stopper abutting part 91 is structured by an end part
481 (one side end part) which is located on the counterclockwise
direction "CCW" side of the gear side protruded part 48. The gear side
protruded part 48 is integrally formed with the body part 44 and is also
integrally formed with the plate-shaped part 43.

[0045] In this embodiment, the plate-shaped part 43 is formed with the
plate-shaped spring 46 and the groove 47 at two positions in the
circumferential direction, and the gear side protruded part 48 is formed
at an angular position corresponding to a portion between the
plate-shaped springs 46 adjacent to each other in the circumferential
direction. Therefore, although an end part on an outer side in the radial
direction of the gear side protruded part 48 is located on an outer side
in the radial direction with respect to a portion on an inner side in the
radial direction of the groove 47, since the gear side protruded part 48
and the groove 47 are displaced from each other in the circumferential
direction, the gear side protruded part 48 and the body part 44 can be
integrally formed with each other. In this embodiment, the gear side
protruded part 48 is formed in a planar shape in which a width dimension
in the circumferential direction on its inner side in the radial
direction is shorter than a width dimension in the circumferential
direction on its outer side in the radial direction. Therefore, a
rotatable angular range of the driven gear 42 is wide. However, it may be
structured that a width dimension in the circumferential direction on an
inner side in the radial direction of the gear side protruded part 48 and
a width dimension in the circumferential direction on its outer side in
the radial direction are equal to each other, or that a width dimension
in the circumferential direction on its inner side in the radial
direction is longer than a width dimension in the circumferential
direction on its outer side in the radial direction.

[0046] The second case member 22 is provided with a support body side
protruded part 28 which is protruded from the end plate part 220 to the
opposite-to-output side "L2". The stopper abutted part 92 is structured
by an end part 281 (the other side end part) on a side in the clockwise
direction CW of the support body side protruded part 28 (the other side
around the turning center axial line "L"). In this embodiment, the
support body side protruded part 28 is protruded from an inner peripheral
face of the cylindrical tube part 227 toward the turning center axial
line "L" of the driven gear 42 on an inner side of the cylindrical tube
part 227, and an end part on an outer side in the radial direction of the
support body side protruded part 28 and the inner peripheral face of the
cylindrical tube part 227 are connected with each other.

[0047] In this embodiment, the support body side protruded part 28 is
provided with a planar shape having a substantially trapezoid and a width
dimension in the circumferential direction on its inner side in the
radial direction is narrower than that on its outer side in the radial
direction. In other words, the support body side protruded part 28 is
protruded from the inner peripheral face of the cylindrical tube part 227
to the inner side in the radial direction along an extended line of the
rib 224a on the inner side of the cylindrical tube part 227. In this
case, a width dimension "W1" on the outer side in the radial direction of
the support body side protruded part 28 is substantially equal to a width
dimension of the rib 224a. However, a width dimension "W2" on its inner
side in the radial direction is set to be narrower than the width
dimension of the rib 224a. In other words, the width dimension "W1" on
the outer side in the radial direction of the support body side protruded
part 28 and the width dimension "W2" on its inner side in the radial
direction are set in the following relationship:

[0048] the width dimension "W1">the width dimension "W2".

[0049] Further, the stopper abutted part 92 (end part 281 of the support
body side protruded part 28) is provided at a position where the driven
gear 42 receives a reaction force in a direction separated from the drive
side gear 41 when the driven gear 42 is turned in the counterclockwise
direction CCW and the stopper abutting part 91 (end part 481 of the gear
side protruded part 48) is abutted with the stopper abutted part 92. More
specifically, when a turning angle range of the driven gear 42 is divided
into a first angular range .theta.1 and a second angular range .theta.2
by an imaginary line "L11" passing through a turning center of the driven
gear 42 (turning center axial line "L") and a rotation center of the
drive side gear 41 (rotation center axial line "L5"), the stopper abutted
part 92 (end part 281 of the support body side protruded part 28) is
disposed in the first angular range .theta.1 in which the stopper
abutting part 91 is moved in a direction so as to come close to the
rotation center of the drive side gear 41 when the driven gear 42 is
turned in the counterclockwise direction CCW.

[0050] Further, the stopper abutted part 92 is provided in an angular
range of 90.+-.60.degree. with respect to the imaginary line "L11" when
viewed from the turning center of the driven gear 42. Especially, in this
embodiment, the stopper abutted part 92 is provided in an angular range
of 90.+-.10.degree. with respect to the imaginary line "L11" when viewed
from the turning center of the driven gear 42. Therefore, when the driven
gear 42 is turned in the counterclockwise direction CCW and the stopper
abutting part (end part 481 of the gear side protruded part 48) is
abutted with the stopper abutted part 92, the driven gear 42 is surely
received with a reaction force in a direction separated from the drive
side gear 41.

Principal Effects in this Embodiment

[0051] As described above, in the geared motor 100 and the pointer type
display device 200 in this embodiment, the stopper mechanism 9 is
provided which determines a movable range of the driven gear 42 when the
driven gear 42 (output member 10) is turned in the counterclockwise
direction CCW. Therefore, the position of the pointer 11 indicating the
zero point can be determined in which the position where the stopper
mechanism 9 is operated is determined as a home position of the driven
gear 42.

[0052] In this embodiment, in the stopper abutting part 91 and the stopper
abutted part 92 which structure the stopper mechanism 9, the stopper
abutting part 91 is an end part 481 of the gear side protruded part 48
which is integrally formed with the body part 44 on an outer peripheral
face of the body part 44 of the driven gear 42. Therefore, the stopper
abutting part 91 is abutted with the stopper abutted part 92 at a
position near the turning center axial line "L" of the driven gear 42.
Accordingly, when the stopper mechanism 9 is operated, collision energy
received by the driven gear 42 is small and thus rebounding of the driven
gear 42 can be restrained. As a result, when the driven gear 42 is turned
in the counterclockwise direction CCW toward the zero point of the
pointer 11 and the zero point is indicated, the pointer 11 is hard to be
shaken. Further, the gear side protruded part 48 is integrally formed
with the plate-shaped part 43 of the driven gear 42 and thus the strength
of the gear side protruded part 48 can be increased.

[0053] The plate-shaped part 43 is formed with the plate-shaped springs 46
at a plurality of positions in the circumferential direction and the gear
side protruded part 48 is formed at an angular position corresponding to
a portion between the plate-shaped springs 46 adjacent to each other in
the circumferential direction. Therefore, even when the plate-shaped
springs 46 are formed in the plate-shaped part 43, restriction of the
position for forming the gear side protruded part 48 is reduced.
Accordingly, the gear side protruded part 48 is easily provided on an
inner side in the radial direction.

[0054] On the other hand, the stopper abutted part 92 is the end part 281
of the support body side protruded part 28 which is protruded toward the
turning center of the driven gear 42 from an outer side in the radial
direction to an inner side in the radial direction, and a width dimension
in the circumferential direction of the support body side protruded part
28 on the inner side in the radial direction is narrower than that on its
outer side in the radial direction. Therefore, even in a case that the
width in the circumferential direction of the support body side protruded
part 28 is set to be wide to some extent for securing strength, when the
stopper mechanism 9 is operated, the stopper abutting part 91 and the
stopper abutted part 92 are abutted with each other at a position which
is near to the turning center of the driven gear 42. Therefore, when the
stopper mechanism 9 is operated, collision energy applied to the driven
gear 42 is small and thus rebounding of the driven gear 42 can be
restrained. Accordingly, when the pointer 11 is turned in the
counterclockwise direction CCW toward the zero point of the pointer 11
and the zero point is indicated, the pointer 11 is hard to be shaken.

[0055] The width dimension in the circumferential direction of the support
body side protruded part 28 is narrower on an inner side in the radial
direction than that on its outer side in the radial direction and thus a
movable range in the counterclockwise direction CCW of the driven gear 42
can be increased. Further, the support body side protruded part 28 is
integrally formed with the cylindrical tube part 227 on an inner side in
the radial direction of the cylindrical tube part 227. Therefore, the
strength of the support body side protruded part 28 (stopper abutted part
92) can be increased.

[0056] In the stopper mechanism 9, when the driven gear 42 is turned in
the counterclockwise direction CCW and the stopper abutting part (the end
part 481 of the gear side protruded part 48) is abutted with the stopper
abutted part 92 (the end part 281 of the support body side protruded part
28), the stopper abutted part 92 is provided at a position where the
driven gear 42 is applied with a reaction force in a direction separated
from the drive side gear 41. More specifically, when the stopper
mechanism 9 is operated, the stopper abutting part 91 is abutted with the
stopper abutted part 92 in the first angular range .theta.1. Therefore,
when the stopper mechanism 9 is operated, engagement of the drive side
gear 41 with the driven gear 42 becomes shallow and thus an inertia
torque in an opposite direction from the drive side gear 41 and the rotor
5 is hard to be transmitted to the driven gear 42. Accordingly,
rebounding of the driven gear 42 can be restrained and thus, when the
pointer 11 is turned in the counterclockwise direction CCW toward the
zero point of the pointer 11 and the zero point is indicated, the pointer
11 is hard to be shaken.

[0057] Especially, in this embodiment, in the first angular range
.theta.1, the stopper abutting part 91 is abutted with the stopper
abutted part 92 in an angular range of 90.+-.60.degree. with respect to
the imaginary line "L11" when viewed from the turning center of the drive
side gear 41. In addition, in this embodiment, in the first angular range
.theta.1, the stopper abutting part 91 is abutted with the stopper
abutted part 92 in an angular range of 90.+-.10.degree. with respect to
the imaginary line "L11" when viewed from the turning center of the drive
side gear 41. Therefore, when the stopper mechanism 9 is operated, the
driven gear 42 is surely applied with a reaction force in a direction
separated from the drive side gear 41. Accordingly, engagement of the
drive side gear 41 with the driven gear 42 becomes shallow and thus an
inertia torque in an opposite direction from the drive side gear 41 and
the rotor 5 is hard to be transmitted to the driven gear 42. As a result,
rebounding of the driven gear 42 can be restrained and thus, when the
pointer 11 is turned in the counterclockwise direction CCW toward the
zero point of the pointer 11 and the zero point is indicated, the pointer
11 is hard to be shaken.

[0058] In addition, the stopper mechanism 9 is structured between the
driven gear 42 integrally turned with the output member 10 and the second
case member 22. Therefore, a movable range in the counterclockwise
direction CCW of the output member 10 (pointer 11) can be directly
restricted by the stopper mechanism 9.

Other Embodiments

[0059] In the embodiment described above, the stopper mechanism 9 is
provided between the second case member 22 of the case 2 (support member)
and the driven gear 42 (second gear). However, the stopper mechanism 9
may be provided between the first case member 21 and the driven gear 42
(second gear).

[0060] In the embodiment described above, the stopper mechanism 9 is
structured between the driven gear 42 and the second case member 22.
However, the present invention may be applied to a case that the stopper
mechanism 9 is structured between the drive side gear 41 and the second
case member 22. In this case, the drive side gear 41 corresponds to the
first gear in the present invention and the pinion 56 corresponds to the
second gear in the present invention.

[0061] In the embodiment described above, the gear train 4 includes two
gears (drive side gear 41 and driven gear 42) in addition to the pinion
58. However, the present invention may be applied to a case that the gear
train 4 includes two gears including the pinion 58, or to a case that the
gear train 4 includes four or more gears including the pinion 58.

[0062] In the embodiment described above, as an example, the geared motor
100 is applied to a pointer type display device 200. However, the present
invention may be applied to a geared motor other than the geared motor
100 for a pointer type display device.

[0063] In the embodiment described above, the output member 10 and the
driven gear 42 are separately provided from each other. However, the
output member 10 and the driven gear 42 may be integrally formed with
each other. In this case, it may be structured that a body part 44 having
a larger diameter than the output member 10 is formed in a root portion
of the shaft-shaped output member 10. Alternatively, it may be structured
that a shaft-shaped output member 10 is protruded from the plate-shaped
part 43 and no body part 44 having a larger diameter than the output
member 10 is formed in a root portion of the output member 10. In a case
that the former structure is adopted, the gear side protruded part 48 is
integrally formed with the body part 44. In a case that the latter
structure is adopted, a root portion of the output member 10 corresponds
to the body part 44 and the gear side protruded part 48 is integrally
formed in the root portion of the output member 10.

[0064] In the embodiment described above, the support body side protruded
part 28 is integrally formed with the cylindrical tube part 227 of the
second case member 22. However, in a case that the cylindrical tube part
227 is not formed, it may be structured that the support body side
protruded part 28 is integrally formed on only the end plate part 220.